Currently, Long Term Evolution (LTE) has been brought into wide commercial use. Carrier Aggregation (CA) technology is introduced in 3GPP R10, and multi-carrier joint scheduling processing is implemented. However, in a data transmission process, real-time transmission from a radio link control (RLC) layer to a Media Access Control (MAC) layer is generally required to be completed within 100 us (microseconds), and therefore relatively high interface bandwidth is required. All currently existing CA solutions are implemented inside a base station, and it is difficult to deploy inter-site CA and inter-board CA because of an interface bandwidth bottleneck.
Specifically, in a case in which inter-site CA deployment cannot be implemented, in an existing CA technology, when transmission of inter-base station data from the radio link control (RLC) layer to the Media Access Control (MAC) layer is limited to be completed within 100 us (microseconds), and a data amount of 4T4R air interfaces at an air interface bandwidth of 20 megahertz is 300 kb (kilobyte), inter-base station interface bandwidth may be calculated as 300 kb/100 us=3 Gbps (Gigabit per second). Generally, data transmission bandwidth that can be provided by an inter-base station interface is 1 Gbps, and the inter-base station interface bandwidth when data is being transmitted is generally greater than 1 Gbps, and therefore inter-site CA deployment cannot be implemented.
In another aspect, despite that all currently existing CA is implemented inside a base station, in an intra-base station and inter-board intra-site CA solution, data is transmitted from a Packet Data Convergence Protocol layer (PDCP) to an RLC layer at a low speed. After scheduling information is received at the RLC layer, the data is transmitted to all MAC layers for at a high speed, and generally the data is limited to be transmitted within 100 us; therefore, a requirement for inter-board interface bandwidth is relatively high. For example, Payload (payload) data is 300 kb, and in an inter-board intra-site CA solution, transmission from the RLC layer to all the MAC layers is limited to be completed within 100 us. Inter-base station interface bandwidth required for transmission from the RLC layer to all the MAC layers is 300 kb/100 us=3 Gbps. Generally, inter-board bandwidth that can be provided for data transmission is 1 Gbps. It can be seen that the inter-board interface bandwidth is greater than the inter-board bandwidth that can be provided for data transmission, and inter-board CA deployment cannot be implemented.
Therefore, it is difficult to implement the CA technology in the prior art because application of the CA technology between devices requires relatively high interface bandwidth.